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AzamSharp Some day I will know everything. I hope that day never comes.

Data Caching allows you to hold the items in the memory (Cache) so you don't have to access the database on each and every request. A common pattern when performing data caching is shown below:

 if (Cache["Rooms"] == null)
                // get the rooms
                var rooms = from r in virtualRoomDC.tblRooms
                            select r;

                Cache["Rooms"].Insert("Rooms", rooms);


            return Cache["Rooms"] as IEnumerable<tblRoom>;

First, we check if the Cache[Key] is null or not. If the Cache[Key] is null then we ask the database for the items. Once, we get the items we put it in the Cache using a Key/Value combination. Now, the next time we request for those items it will be loaded from the Cache and not fetched from the database. This greatly reduces the load on the database server and hence improve performance.

I think it will be very beneficial if we could achieve the same pattern using the minimum amount of code. For this purpose I created a custom attribute called CacheAttribute which when placed on a method caches the result of the method. The CacheAttribute takes a single argument which is the cache time in seconds. Take a look at the CacheAttribute implementation below:

    public class CacheAttribute : System.Attribute
        private int _timeInSeconds;

        public CacheAttribute(int timeInSeconds)
            _timeInSeconds = timeInSeconds;

        public int TimeInSeconds
            get { return _timeInSeconds; }
            set { _timeInSeconds = value; }

Now, to use the CacheAttribute I will just place it on the method as show below:

        public IEnumerable<tblRoom> GetAllRooms()
                // get the rooms
                var rooms = from r in virtualRoomDC.tblRooms
                            select r;               

                return rooms;

This means that the result of the GetAllRooms method will be cached for "10" seconds. Now, let's call this method from the UI.

var time = (DateTime) MethodInvoker.Invoke<RoomRepository>("GetAllRooms", null);

Currently, I am returning the cached datetime object but practically you will return the return parameter of the method invoked. Here is the implementation of the MethodInvoker class.

 public static object Invoke<T>(string methodName, object values)
            if (HttpContext.Current.Cache.Get(methodName) == null)
                Type t = typeof(T);

                MethodInfo method = t.GetMethod(methodName);
                CacheAttribute cacheAtt = (CacheAttribute)method.GetCustomAttributes(typeof(CacheAttribute), false)[0];

                object o = Activator.CreateInstance(t);
                object result = null;

                if (values != null)
                    result = method.Invoke(o, new object[] { values });

                HttpContext.Current.Cache.Insert(methodName, DateTime.Now, null, DateTime.Now.AddSeconds(cacheAtt.TimeInSeconds), TimeSpan.Zero);

            return HttpContext.Current.Cache[methodName];

Once, again I am putting the cached datetime into the HttpContext.Current.Cache but you will put the result of the method call. Now, when I call this method multiple times I will get the cached data for the first 10 seconds. Once the cache time is expired I will get the fresh copy from the database. Take a look at the screen shot below:DynamicCacheUSingAtteibute

Posted on Saturday, February 16, 2008 10:09 AM | Back to top

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